abstract: High Voltage Direct Current (HVDC) technology is being considered for several long distance point-to-point overhead transmission lines, because of their lower losses and higher transmission capability, when compared to AC systems. Insulators are used to support and isolate the conductors mechanically and electrically. Composite insulators are gaining popularity for both AC and DC lines, for the reasons of light weight and good performance under contaminated conditions. This research illustrates the electric potential and field computation on HVDC composite insulators by using the charge simulation method. The electric field is calculated under both dry and wet conditions. Under dry conditions, the field distributions along the insulators whose voltage levels range from 500 kV to 1200 kV are calculated and compared. The results indicate that the HVDC insulator produces higher electric field, when compared to AC insulator. Under wet conditions, a 500 kV insulator is modeled with discrete water droplets on the surface. In this case, the field distribution is affected by surface resistivity and separations between droplets. The corona effects on insulators are analyzed for both dry and wet conditions. Corona discharge is created, when electric field strength exceeds the threshold value. Corona and grading rings are placed near the end-fittings of the insulators to reduce occurrence of corona. The dimensions of these rings, specifically their radius, tube thickness and projection from end fittings are optimized. This will help the utilities design proper corona and grading rings to reduce the corona phenomena. / Dissertation/Thesis / M.S. Electrical Engineering 2013

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-06-29T11:48:02Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação de Mestrado - Lívia Rodrigues e Brito.pdf: 11880513 bytes, checksum: cdf56fe284940b9c31e62271753b913f (MD5) / Made available in DSpace on 2016-06-29T11:48:02Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação de Mestrado - Lívia Rodrigues e Brito.pdf: 11880513 bytes, checksum: cdf56fe284940b9c31e62271753b913f (MD5) Previous issue date: 2014-08-25 / CNPq / A adição de aditivos detergentes dispersantes nas gasolinas brasileiras será obrigatória a partir de julho de 2015. É necessário, portanto, desenvolver uma metodologia que permita quantificar esses aditivos para verificar o cumprimento da lei. Neste trabalho, é proposto um método que associa a técnica do ring-oven com as imagens hiperespectrais no infravermelho próximo (NIR-HI). Como os aditivos são adicionados em baixas concentrações, a técnica do ring-oven foi empregada para concentrá-los previamente à análise por NIR-HI. Anéis foram produzidos a partir de amostras de gasolinas comum adicionadas dos aditivos (denominados G, T, W e Y) fornecidos pela Agência Nacional do Petróleo, Gás Natural e Biocombustíveis (ANP) e as imagens adquiridas utilizando uma câmera hiperespectral (SisuCHEMA). Três estratégias de extração dos espectros do anel foram testadas a fim de se escolher a mais rápida e objetiva. A estratégia escolhida se baseia nos histogramas dos escores da primeira componente principal das imagens analisadas individualmente. Modelos de calibração individuais para cada aditivo foram construídos empregando a regressão por mínimos quadrados parciais (PLS), por isso, fez-se necessária uma etapa prévia de classificação. O melhor resultado para classificação foi obtido empregando a análise discriminante linear (LDA) associada ao algoritmo genético (GA) para seleção de variáveis, o qual apresentou uma taxa de classificações corretas de 92,31 %. Observou-se que a maioria dos erros de classificação envolveram amostras dos aditivos G e W. Um único modelo de regressão para esses dois aditivos foi, então, construído e seu erro foi equivalente aos dos modelos individuais. Os modelos de regressão apresentaram erros médios de predição entre 2 e 15 %. Esses resultados mostram que a metodologia proposta pode ser utilizada para determinar as concentrações dos aditivos com confiabilidade e garantir que eles estão sendo adicionados conforme a lei. / The addition of detergent dispersant additives to Brazilian gasoline will be mandatory from July 2015. It is necessary, therefore, to develop a methodology that allows quantifying these additives to verify their compliance with the law. In this work, a method that associates the ring-oven technique with near infrared hyperspectral images (NIR-HI) is proposed. Because the additives are added in low concentrations, the ring-oven technique was employed to concentrate them prior to the NIR-HI analysis. Rings were produced from samples of gasolines without additives spiked with additives (called G, T, W and Y) provided by the National Agency of Petroleum, Natural Gas and Biofuels (ANP) and the images were acquired using a hyperspectral camera (SisuCHEMA). Three strategies for extraction of the ring spectra were tested in order to select the faster and most objective. The chosen strategy is based on the histograms of the first principal component scores of the images analyzed individually. Regression models were built for each additive using partial least squares (PLS) regression, so it was necessary to have a previous classification stage. The best classification result was obtained using the linear discriminant analysis (LDA) associated with the genetic algorithm (GA) for variable selection, which showed a correct classification rate of 92.31 %. It was observed that most of the misclassification errors involved the samples of the G and W additives. A single regression model was then built for these two additives and its error was equivalent to the errors of the individual models. The regression models showed average prediction errors between 2 and 15 %. These results show that the proposed methodology can be used to determine the additive concentrations with reliability and to ensure that they are been added according to the law.

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Orientador: Celio Pasquini / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-26T13:37:44Z (GMT). No. of bitstreams: 1 FariasFilho_BeneditoBatista_D.pdf: 5266552 bytes, checksum: 237a6af16ec6a610644e50129eb718d9 (MD5) Previous issue date: 2014 / Resumo: A determinação direta de amostras líquidas utilizando a técnica de Espectroscopia de Emissão Óptica em Plasma Induzido por Laser (LIBS) é muito difícil devido aos limites de detecção insuficientes obtido. Procedimentos de pré-concentração, como o ring oven, permitem que o analito seja determinado a partir de técnicas que utilizam a microanálise como o LIBS, depois da sua transferência para um substrato sólido (papel de filtro). Embora esta abordagem tenha sido praticamente descrita na literatura, o procedimento de medida foi feito manualmente. Assim, neste trabalho foi desenvolvido um sistema de medida mecanizado para analisar por LIBS o conteúdo do anel produzido pela técnica ring oven visando melhorar a precisão e reduzir o tempo de análise. O sistema é composto por um motor contínuo que gira uma plataforma a 10 rpm constituída por um disco de teflon® adaptado ao seu eixo central e que serve como suporte para amostra. A câmara de ICCD do sistema de detecção do LIBS foi programada para integrar o sinal produzido por 120 pulsos do laser que são disparados espaçados uniformemente sobre o contorno do anel durante 6 segundos. Para preparo dos anéis, 60 µL das soluções ou amostras de cachaça eram dispensadas sobre o papel de filtro com vazão de 25 µL min-1 e, em seguida, lavadas com 45 µL de HCl 0,05 mol L-1. Foi utilizado lítio (2 mg L-1; 670,80 nm) como padrão interno para construção das curvas analíticas na faixa de 0 a 8 mg L-1 de cobre (324,75 nm). O padrão interno foi efetivo para corrigir as falhas de amostragem ao longo do contorno do anel durante o processo de medida. As curvas analíticas construídas foram lineares (r > 0,990) na faixa de concentração estudada e o limite de detecção e de quantificação foram de 0,3 mg L-1 e 1,0 mg L-1, respectivamente. Os resultados da determinação de cobre em oito amostras de cachaça mostraram-se estatisticamente indistinguíveis, em nível de 95% de confiança, quando comparados com aqueles obtidos por meio do método oficial de adição de padrão e medidos por espectrometria de absorção atômica em chama (FAAS), com precisão média relativa de 9%. O procedimento de pré-concentração necessitou menos que seis minutos enquanto que as medidas do anel formado, usando o sistema mecanizado, necessitaram no total de dois minutos adicionais. Além disso, foi verificada a potencialidade da técnica ring oven/LIBS para classificação geográfica, por meio de modelos multivariados quimiométricos (LDA, PLS-DA e SIMCA) de cachaças da região de Salinas (MG). A capacidade preditiva das amostras foi melhor para o modelo quimiométrico baseado em Análise Discriminante Linear (LDA), conseguindo classificar corretamente 70% das amostras / Abstract: Direct determination of liquid samples using the technique of Laser-induced breakdown spectroscopy (LIBS) is very difficult due to the insufficient detections limits attained. Procedures of preconcentration, such the ring oven, allow the determination of analyte by microanalysis techniques, after transferring it to a solid substrate (filter paper). Although this approach has been previously described in the literature, the measurement procedure was performed manually. Thus, in this work a mechanized measurement system was developed to analyze by LIBS the contents of the ring produced through the ring oven technique in order to improve the precision and reduce the analysis time. The system consists of a continuous motor that spinning a platform at 10 rpm constituted by a teflon® disc coupled to its axis, serving as a support for the sample. The ICCD camera of the detection system of LIBS was programmed to integrate the signal generated by 120 laser pulses that is fired uniformly spaced on the ring contour during 6 seconds. To prepare the rings, 60 µL of standard solutions or samples of cachaça were dispensed on the filter paper at flow rate of 25 uL min-1 and afterwards washed with 45 µL of HCl 0.05 mol L-1 (42% v/v ethanol). Lithium (2 mg L-1, 670.80 nm) was used as internal standard for the construction of analytical curves in the range from 0 to 8 mg L-1 of copper (324.75 nm). The internal standard was effective to correct the sampling failures around the contour of the ring during the measurement process. Analytical calibration curves were linear (r> 0.99) in the concentration range studied and the limits of detection and quantification were of 0.3 mg L-1 and 1.0 mg L-1, respectively. The results of determination of copper in eight samples of cachaça showed be statistically indistinguishable, at 95% confidence level when compared with the official method of standard addition and measurement by flame atomic absorption spectroscopy (FAAS), with an average relative precision of 9%. The procedure carry out of preconcentration requires less than six minutes, while the measurements of the formed ring, using the mechanized system, requires an total two minutes to be performed. Moreover, it was verified the potentiality of ring oven/LIBS technique for geographic classification of cachaça of Salinas region (Minas Gerais State) using chemometric multivariate modeling (LDA, SIMCA and PLS-DA). The better predictive performace was attained by the chemometric model basead Linear Discriminant Analysis (LDA), achieving correctly classification of 70% of the samples / Doutorado / Quimica Analitica / Doutor em Ciências

Selective protein degradation by the ubiquitin-proteasome system is essential for cellular homeostasis and the regulation of diverse biological processes. The selectivity of this system is imparted by hundreds of ubiquitin ligases that specifically recognise substrates and catalyse their ubiquitination, thereby targeting them for degradation. Among ubiquitin ligases, multisubunit cullin-RING ubiquitin ligases constitute the largest group. However, despite significant advances in understanding their assembly, regulation, and molecular architecture, the substrates and functions of most of them remain unknown. This thesis focuses on two ubiquitin ligases from the cullin-RING ubiquitin ligase 4 (CRL4) subfamily: CRL4DCAF4 and CRL4DCAF12 . To identify their candidate substrates and to address their biological roles, several different approaches have been employed. First, proteomic screening revealed a wide range of candidate substrates. Next, detailed characterisation of the identified interactions and exploration of the condition under which candidate substrates undergo degradation was performed. Finally, knockout human cell lines and mice with a targeted disruption of genes encoding DCAF4 and DCAF12 were generated to explore the physiological roles of CRL4DCAF4 and CRL4DCAF12 . In summary, the herein...

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The purpose of this investigation was to provide a systematic study of the cycloaddition pf (N-alkyl-N-phenylamino)- methoxy-and dichloroketenes to various imines and to investigate the stereochemistry of these cycloadditions.